From the graph, chords HL and HK are equidistance from the center, then they are congruent.
The radius PJ is perpendicular to the chord HK, then PJ bisects HK. This means that:
HN = HK/2
HN = 42/2
HN = 21
PM and PN are congruent, then
PN = PM
PN = 12
In the right triangle PNH, the measure of the angle HPN can be found as follows:

The central angle HPJ (which is the same as angle HPN) and the arc HJ are congruent, then:
